Jig for selective hardening of steel rings



Oct. 2, 1956 T. MUNGALL, SR 2,765,161 I JIG FOR SELECTIVE HARDENING OF sc am macs Filed June 5, 1952 I I II I Ill IN VEN TOR.

F 15 -4 THO/ms MUNGALL s42 ii zmfllwmik A TTOQVE Y JIG FOR SELECTIVE HARDENING OF STEEL RINGS Thomas Mungail, Sr., Cleveland, Ohio, assignor of fifty percent to William Mungall, Dayton, Ohio Application June 3, 1952, Serial No. 291,407

1 Claim. (Cl. 266-6) This invention relates to the process of making armatures for use in electric clocks of the type described in United States Patent No. 2,455,134, granted to me on November 30, 1948. More particularly this invention relates to the method of making and treating the endless metal rings of the said armatures.

In the past, attempts have been made to provide electric clock motors with permanently magnetized rotors. This was done by either perforating, denting, distorting,

. or mutilating the armature rings at points where magnetic poles were desired. The desired eflects were obtained only in a limited degree and the physical distortion created disadvantages which limited the use of the motor for certain purposes and under certain conditions.

It is therefore the primary object of this invention to provide a method of making, treating, hardening and permanently magnetizing and polarizing the rotor rings of synchronous electric motor armatures without distorting, mutilating or otherwise unbalancing or disturbing the uniform operation of the armatures.

This and other objects of the invention will become apparent from a reading of the following specification and claim, together with the accompanying drawing in which:

Figure 1 is a perspective view of a simple endless rotor ring used in the formation of a clock motor armature;

Figure 2 is a perspective view of the jig used for holding the ring during one stage of its manufacture;

Figure 3 is a cross-sectional view of the jig shown in the Figure 2 with the ring of Figure I inserted therein;

Figure 4 is a top plan view of a fixture used for magnetizing and polarizing the hardened sections of the ring; and

Figure 5 is a cross-sectional view taken along the line and in the direction of the arrows 55 of the Figure 4.

The complete motor and armature of which the ring (Whose novel method of production is the subject of this invention) is a part, is completely described in the aforesaid United States Patent No. 2,455,134. The armature ring is shown in the Figure 1 and is identified herein as well as in the drawing of said patent by the reference numeral 31.

The armature ring 31 is an endless band having a width substantially greater than its thickness. It must be made of high grade magnetizable steel having a high hysteresis coefiicient and one which retains its magnetism and its pre-determined fixed polarity. It is provided with a small head 36 around its forward edge which facilitates mounting and assembly with other parts of the armature. It has been determined that the ring must be made of carbon steel having a carbon content ranging between 0.90% and 1.05% and known in the United States as S. A. E. No. 1095 Steel. Swedish Steel of this analysis is even better for the purpose, but difiicult to obtain.

The heat treating and tempering jig 40 shown in the Figure 2 is a solid piece of cast iron or other durable metal having a thickness substantially greater than the width of the ring 31. It has a central hole 41 therenited States Patent 0 through, which hole has a diameter the same as the outside diameter of the ring 31. This hole 41 should be of such size that it will neatly and snugly receive and retain the said ring. Cut into the jig 40 and extending radially around the central hole 41 there are eight evenly spaced slots 42. The slots 42 have a uniform width and determine the width of the hereinafter described polarized sections of the ring. This jig is also provided with a metal strip 43 which serves as a handle or holder for the jig.

When making an armature ring by the process embodied in this invention, the ring 31 is first marked with a small dot of paint or suitable ink to identify a specific pole position. The ring is then inserted in the jig 40 with the locating dot centered in one of the slots 42. The jig and the ring nested therein are then heated by a flame or any other suitable means to a temperature between 1450" and 1475 Fahrenheit. The jig and ring are then immersed bodily in a quenching bath. This may take any suitable form, but the preferred bath is a quantity of light petroleum oil of SAE 40 weight. This oil is kept at room temperature and the jig is plunged into the oil and kept there for approximately one minute, after which it is removed and permitted to air cool.

The parts or section 32 of the ring which face the slots are quickly chilled by the quenching liquid which can instantly reach all surfaces of such unprotected sections, thereby hardening such sections of the ring. The intermediate sections are protected from contact with the quenching fluid by the jig bore face 41. At the same time, any sudden heat loss from contact with the quenching fluid in the protected areas of the ring is prevented by heat flowing into such portions of the ring through their contact with the great mass of heat stored up in the metal of the jig. These intermediate sections are therefore cooled slowly in the air after the jig is removed from the quenching bath and remain relatively softer than the chilled section 32, and are less able to hold any magnetism applied thereto.

The magnetizing fixture shown in the Figures 4 and 5 comprises a non-magnetic base 54 made of wood, brass or other suitable material on which there are mounted four electromagnets 51 connected to a source of 6-volt direct current. The magnets are arranged and spaced as shown and held in place by means of the brackets 52 so that the north and south poles thereof alternate around a circle as shown. The ends of the pole pieces are shaped so that the armature ring 31 may be snugly fitted in the opening so formed in contact with all of the pole pieces of the four electromagnets 51. The spacing and width of the poles coincide with the spacing and width of the slots 42 of the jig 40.

After the ring 31 in the jig 40 is cool enough to handle, it is removed therefrom and inserted in the jig 50 between the pole pieces as shown in the Figures 4 and 5 and so oriented that the marked spot which indicates a hardened section is aligned with one of the poles of a magnet. The magnets are then energized for approximately one second which is sufiicient for the hardened sections 32 of the ring to become permanently magnetized. While electromagnets are used in the preferred method, a set of four permanent magnets suitably arranged could be used to magnetize the ring, if so desired.

The magnetized ring, thereafter is, in effect, and actually is four bar magnets joined evenly and in balance. That is, the polarized portions of the ring are evenly spaced apart and the flux flow is uniform through the unmagnetized soft sections of the ring.

After being so treated and magnetized, the armature ring is mounted on the arbor of the armature. From all outward appearances this armature ring looks like an untreated and unmagnetized ring. No apparent physical change has taken place; By using this process for creating the spaced magnetic poles, no physical deformation of the ring occurs and its mechanical continuity and balance are not impaired, thereby assuring a true running armature with long life characteristics.

Having thus disclosed the preferred methods of treating andpolarizing the rotor rings, it should be understood that there may be other methods for heat treating and polarizing and therefore no limitations are intended hereby except those imposed by the appended claim.

I claim:

A jig for forming spaced hardened sections in a circular steel ring, comprising a circular iron body of great mass and of a thickness greater than the ring to be hardened, having a central hole of a diameter to snugly receive the ring therein, during the entire heating and quenching-cycle the said body also having spaced radially 4. extending slots extending outwardly from the said hole but stopping short of the periphery of the body, the width and spacing of said slots corresponding to the Width and spacing of the hardened sections to be formed in the aforesaid ring.

References Cited in the file of this patent UNITED STATES PATENTS 153,115 Robinson July 18, 1874 220,681 Le Doyt Oct. 14, 1879 232,112 Brown et al. Sept. 14, 1880 442,065 Low Dec. 2, 1890 1,715,713 Legg June 4, 1929 1,848,364 Legg Mar. 8, 1932 2,572,201 Rooke Oct. 23, 1951 

